1. Field of the Invention
The present invention relates to an image pickup apparatus and a focusing method.
2. Description of the Related Art
A phase difference detecting method is known as an autofocusing (“AF”) method. Japanese Patent Laid-Open No. (“JP”) 2009-244429 proposes an image pickup apparatus that includes an image pickup element that has focus detecting pixels and is configured to provide a phase difference AF on an image pickup plane, and a dedicated sensor that provides a phase difference AF on a secondary imaging plane. Other prior art include JP 2001-174690, 2001-128044, and 2005-12307.
Since focus detecting data from the dedicated sensor represents the just previous state of the image pickup, the focus detecting data generated by the dedicated sensor at the focus detecting time does not correspond to a captured image when an object is a moving body, due to a time lag from the focus detection to image pickup. As a result, the in-focus precision deteriorates. Although there are conventionally demands for the improved in-focus precision in the phase difference AF using the dedicated sensor, none of prior art propose effective means for improving the in-focus precision using the dedicated sensor.